The present invention relates to a scroll-type compressor machine in which a stationary scroll and an orbiting scroll cooperate with each other to compress a volume of fluid.
Before describing the present invention, principles of a scroll compressor will be described briefly.
Fundamental components of the scroll compressor are shown in FIGS. 1A to 1D, in which reference numeral 1 denotes the stationary scroll, 2 the orbiting scroll, P a compression chamber formed between the stationary scroll 1 and the orbiting scroll 2, and O the center of the stationary scroll 1.
The stationary scroll 1 and the orbiting scroll 2 have wraps which are the same in configuration except for the direction in which the wraps are wound. Each wrap is composed of a combination of involutes and arcs. The compression chamber P is formed between the wraps when they are assembled.
The operation of this compressor will be described. In FIG. 2, the stationary scroll 1 is stationary spatially and the orbiting scroll 2 is combined with the stationary scroll 1 as shown. The orbiting scroll 2 rotates, i.e., orbits, around the center O of the stationary scroll 1 without changing its spatial attitude i.e., without rotating around its own axis, through positions shown in FIGS. 1A through 1D sequentially. With such movement of the orbiting scroll 2, the volume of the compression chamber P is reduced gradually so that air received at an outside position into the compression chamber P is compressed and discharged near the center portion of the stationary scroll 1 at which the degree of compression becomes maximum.
A typical example of the conventional scroll-type compressor will be described with reference to FIG. 2. The scroll compressor shown in FIG. 2 is applied to, for example, a refrigerator, an air conditioner or an air compressor, in which it is adapted to compress a gas such as Freon gas. In this figure, 1 is a stationary scroll, 2 is an orbiting scroll, and 201 is a base plate of the orbiting scroll 2. 204 is an orbiting scroll shaft, P is a compression chamber, 104a is a suction portion of the compression chamber, 616 is a ring mounted on the base plate 201 with a small gap between it and a rear surface of the base plate 201, and 8 is an Oldhams coupling in the form of a ring which is adapted to prevent the orbiting scroll 2 from rotating around its axis while permitting its orbital movement. The Oldhams coupling 8 has a pair of oppositely arranged protrusions 802 on each surface, the protrusion pair on one surface being orthogonal to the protrusion pair on the other surface.
601 is a thrust bearing for supporting the rear surface of the base plate 201 of the orbiting scroll. 670 is a bearing support to which the stationary scroll 1 is fixed by bolts, etc., and which is fixed to a shell by pressure fitting etc., the shell beind described later. 605 is a chamber defined by the base plate 201, the ring 616 and the bearing support 670 for housing the Oldhams coupling, 604 is an oil return path connecting the chamber 605 and a motor chamber to be described. 11 is a stator of a motor mounted on the bearing support 670, 10 is a rotor of the motor. 4 is a crankshaft, 404 is an oil hole provided eccentrically in the crankshaft 4, 5 is an orbiting scroll bearing provided eceentrically in the crankshaft 4 for supporting the orbiting scroll shaft 204. 602 is a main bearing for supporting an upper portion of the crankshaft 4. 702 is a bearing for supporting an intermediate portion of the crankshaft 4. 402 is a first balancer fixed on an upper portion of the rotor 10. 403 is a second balancer fixed on a lower portion of the rotor 10. 9 is the shell supporting the bearing support 670, the shell 9 being adapted to seal air-tightly the whole of the compressor. 909 is an oil reservoir provided at a bottom of the shell 9. 904 is a suction pipe communicating a motor chamber 912b with the atmosphere outside the shell 9. 614b is a fluid path formed partially between the bearing support 670 and the shell 9. 905 is a discharge pipe for discharging gas around the center of the scroll 1 to the outside of the shell 9, and 10e is an air path passing through the rotor 16b.
The operation of the scroll compressor constructed as above will be described.
When power is supplied to the stator 11 of the motor, the rotor 10 thereof produces a torque sufficient to drive the crankshaft 4. When the crankshaft 4 starts to rotate, torque is transmitted to the orbiting scroll shaft 204, supported by the orbiting bearing 5 provided eccentrically on the crankshaft 4, and the orbiting scroll 2 orbits, guided by the Oldhams coupling 8, so that compression is obtained as explained with reference to FIGS. 1A to 1D. Gas introduced through the suction pipe 904 to the motor chamber 912b passes through an air gap formed between the stator 11 and, the rotor 10 and the air path 10e while cooling them. The direction of gas flow is changed near the oil reservoir 909, afterwards passing through the path 614b to the suction chamber 104a and then to the compression chamber P. In the compression chamber P, the gas is forced gradually to the center of the stationary scroll 1 upon rotation of the crankshaft 4, and discharged finally through the discharge pipe 905 provided in the center portion.
Describing the oil supply system, a lubrication oil 909a from the oil reservoir 909 is forced, by the pumping action of the oil path 404 provided eccentrically in the crankshaft 4, to move from a lower end of the crankshaft 4 through the oil path 404, the orbiting bearing 5 and the main bearing 602 to the motor bearing 702 (as shown by a dotted arrow) and, after passing through the thrust bearing 601, discharged to the Oldhams chamber 605. The oil in the Oldhams chamber 605 drops through the oil return path 604 to the motor chamber 912b and, after passing through the air gap between the stator 11 and rotor 10, returns to the oil reservoir 909.
The orbital movement of the orbiting scroll 2 due to the rotation of the crankshaft 4 tends to vibrate the compressor because the latter may have an unbalanced structure. However, since the first and second balancers 402 and 403 act to balance the crankshaft 4 and associated parts thereof, the compressor can operate without abnormal vibration.
Such a conventional scroll-type machine, however, is defective due to the fact that the balancers 402 and 403 are mounted on the rotor 10. The crankshaft is subject to a large bending moment due to centrifugal forces acting on the balancers, resulting in uneven radial forces acting on the main bearing 602 and the motor bearing 702, which degrades the reliability of the apparatus. The conventional scroll-type compressor further encounters the problem that an eccentric bushing, which rotatably receives the shaft and is intended to seal the compressor chamber while providing a path for lubricating oil, may be lifted by the pump head or the like during operation and may be excessively rotated, thereby causing insufficient compression.